Lock nut
This application is a continuation of abandoned application Ser. No. 071,542, filed Jul. 7, 1987, which is a continuation of abandoned application Ser. No. 830,240, filed Feb. 18, 1986, which is a continuation of abandoned application Ser. No. 675,249, filed Nov. 26, 1984, which is a continuation of abandoned application Ser. No. 303,104, filed Sep. 17, 1981. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention relates, to a lock nut in which an annular flat plate such as made of sheet metal for spring is secured on one surface of a nut and, more specifically, this invention relates to a lock nut for use in setting a rolling bearing mounted on a shaft. Such a lock nut is adapted so that the projection of the annular flat plate firmly contacts the threaded surface of a thread member such as a bolt or a threaded shaft for obtaining satisfactory locking effect of the nut due to frictional action. 
     It is desired that the locking effect of the nut may not be reduced even after the repeated screw-engagement of the lock nut with the thread member. If plastic deformation is caused to the annular flat plate which is to be in firm contact with the threaded surface of the male thread on a shaft after the repeated screw-engagement of the nut with the male thread on the shaft, desired firm contact with the male thread of the shaft will no more be obtained. Thus, it is required that the, annular flat plate be made of resilient material such as sheet metal for spring. 
     Lock nuts have hitherto been known in which a plurality of arcuate protrusions are symmetrically formed on an inner periphery of an annular flat plate and they are contacted with the threaded surface of a bolt, each top of the arcuate protrusions defined on a circle concentrical with the circle to which the periphery of the annular flat plate is associated. 
     In such a lock nut, however, since the symmetrically disposed protrusions contact the threaded surface of the male thread individually, they can not provide so great interferring pressure to the male thread and thus the lock nut is loosened from the bolt when vibrations are exerted on an article to be fastened by the lock nut and the bolt. Particularly, in a case where the lock nut is employed for setting the rolling bearing mounted on a shaft, the lock nut often loosens due to the rotation and the vibration of the shaft. 
     This invention has been made in view of the foregoing defects and the object thereof is to provide a lock nut for use with a thread member such as a bolt, particularly for use in setting a rolling bearing mounted on a shaft, in which a single protrusion is formed asymmetrically to an annular flat plate so that the protrusion of the flat plate may firmly contact the threaded surface on the thread member such as the bolt or the shaft, and the protrusions intensely bear against the threaded surface of the male thread to thereby surely prevent the nut from loosening. 
     In the lock nut according to this invention, an annular flat plate secured on one surface of a nut is provided at its inner periphery with an asymmetrical single arcuate protrusion and the protrusion is extended in the form of an arc inwardly over the one-half or more portion of the inner periphery of the annular flat plate integrally, and the annular flat plate secured on one surface of a nut has means for preventing a relative sliding movement of the flat plate to the nut. When the lock nut is screwed to a thread member, the top end of the protrusion of the annular flat plate contacts firmly and continuously the spiral threaded surface corresponding to more than one-half pitch of the male thread on the thread member and exerts intense interfering pressure to the threaded surface, whereby the lock nut can effect reliable locking action. The arcuate protrusion may be defined on a circle concentrical with the circle to which a periphery of the annular flat plate is associated. 
     Particularly, in the lock nut according to this invention, since the asymmetrical arcuate protrusion of the annular flat plate deforms elastically and screw-engages eccentrically with the male thread of the thread member upon screw engagement of the nut with the thread member, the arcuate protrusion applies an intense interfering pressure on the threaded surface of the male thread and also applies such a force to the nut that the female thread of the nut and the male thread of the thread member firmly contact to each other at each of their flank surfaces. 
    
    
     This invention is to be described by way of preferable embodiments referring to the accompanying drawings, wherein 
     FIG. 1 is an upper plan view of a lock nut according 1 to this invention, 
     FIG. 2 is a bottom view of the lock nut according to this invention, 
     FIG. 3 is a front elevational view of the lock nut according to this invention, 
     FIG. 4 is a cross sectional view taken along line 4--4 in FIG. 1, 
     FIG. 5 is an upper plan view for another embodiment according to this invention, 
     FIG. 6 is an upper plan view of an annular flat plate, 
     FIG. 7 is a front cross sectional view of the annular flat plate, 
     FIG. 8 is an explanatory cross sectional view of the lock nut according to this invention when it is screwed with a male thread member, 
     FIG. 9 is an explanatory cross sectional view for another embodiment of the annular flat plate, 
     FIG. 10 is an upper plan view for still another embodiment of the lock nut according to this invention, 
     FIG. 11 is a front cross sectional view of the lock nut shown in FIG. 10, 
     FIG. 12 is a plan view showing another embodiment of the annular flat plate, 
     FIG. 13 is an enlarged cross sectional view taken along line 13--13 in FIG. 12, 
     FIG. 14 is a plan view showing a further embodiment different from the annular flat plate in FIG. 12, 
     FIG. 15 is an enlarged cross sectional view taken along line 15--15 in FIG. 14, 
     FIG. 16 is an enlarged cross sectional view taken along line 16--16 in FIG. 14, 
     FIG. 17 is an explanatory cross sectional view of a part of the annular flat plate shown in FIG. 12 where it is secured on one surface of the nut, and the nut is screwed on a male thread member, 
     FIG. 18 is an explanatory cross sectional view of a part of the annular flat plate shown in FIG. 14 where it is secured on one surface of the nut, and the nut is screwed on a male thread member, and 
     FIG. 19 is a cross sectional view taken along line 19--19&#39; in FIG. 18. 
    
    
     As shown in FIG. 1 to FIG. 4, the lock nut according to this invention comprises a round nut 1 and an annular flat plate 3 abutted against the upper surface 2 thereof, the annular flat plate 3 being secured between the upper surface 2 and the cylindrical portion 4 of the nut by means of caulking a cylindrical portion 4 projected from the upper portion of the nut 1 inwardly and downwardly. 
     The round nut 1 is symmetrically formed at its outer circumference with four axially extended cut away grooves 5 in which an appropriate tool is positioned to screw the nut 1 to the male thread formed on a thread member such as a bolt or a shaft. 
     The annular flat plate 3, is formed with material having high yield point, for example, sheet metal for spring such as high carbon steel, stainless steel and phosphor bronze. As shown in FIG. 6 and FIG. 7, the annular flat plate 3 comprises an annular circumferential periphery 6 and an arcuate protrusion 7 extended inwardly and integrally from the circumferential periphery 6, and the circumferential periphery 6 is held between the upper surface 2 and the cylindrical portion 4 of the nut. The arcuate protrusion 7 is protruded from the portion substantially corresponding to 3/4 of the inner circumference of the periphery 6 to the center P for the periphery 6. That is, the arcuate projection 7 of about 270° angle is formed. The inner diameter of the arcuate protrusion 7 is substantially equal to the root diameter of the male thread 8 on a thread member B to which the nut 1 is screwed. Accordingly, the top end 9 of the protrusion 7 is protruded slightly inward of the top of the crest of the female thread 10 on the nut 1. As shown in FIG. 8, the top end 9 may be rounded to be fitted with the root 11 of the male thread 8 and it is preferred to set the length of the protrusion 7 to such an extent as the arcuate protrusion 7 slightly deflects upon contact of the top end 9 to the root 11. 
     In FIG. 8, the lock nut is shown to include a cylindrical portion (16) having first (56), second (57) and third (58) portions, the first portion having first (59) and second (60) ends, the first end of the first portion being integrally connected to the first end of the circular nut body (61) near the outer periphery of the annular surface of the first end (64) of the nut body (61) and extending from the annular surface of the first end of the nut body in an axial direction from the body, the second portion (56) having an inverted &#34;U&#34; shape, and having first (62) and second (63) ends, the first end of the second portion being integrally connected to the second end of the first portion, bending inwardly from the second end of the first portion toward the center of the circular nut body (61), the third portion (58) having first (65) and second (66) ends, the first end of the third portion (58) being integrally connected to the second end of the second portion and extending from the second end of the second portion in an axial direction toward the nut body. 
     The female thread 10 of the nut 1 terminates adjacent the upper surface 2 and it is preferred to position the protrusion 7 of the annular flat plate 3 in association with the terminating point. Specifically, one corner 7a of the protrusion is positioned at a point moved adversely to the forwarding direction of the spiral of the female thread 10 by 90° from the terminating point. The protrusion 7 has an arc of 270° angle beginning from the corner 7a and terminating at the other corner 7b. FIG. 1 shows a female thread 10 with right hand thread. 
     Upon screw-engagement of the lock nut 1 having the foregoing constitution with the thread member B, the top end 9 of the arcuate protrusion 7 is fitted to the flank surface or root 11 of the male thread 8, whereby the arcuate protrusion 7 is deformed elastically and contacts firmly the flank surface of the male thread 8, and the top end 9 of the protrusion 7 eccentrically presses the flank surface of the thread member B inwardly in the radial direction, as well as downwardly in the axial direction. 
     In addition, since the arcuate protrusion 7 is extended from the portion corresponding to 3/4 of the inner circumference of the circumferential periphery 6, the protrusion 7 firmly comes into contact with the threaded surface corresponding to 3/4 pitch of the male thread 8. Further, since the arcuate protrusion 7 is formed asymmetrically, the annular flat plate 3 is screwed eccentrically with the male thread 8 and the female thread 10 of the nut 1 also causes interference on the male thread 8 to set the nut 1 to the thread member B in an eccentric state, so that the plate 3 securely prevents the nut 1 from loosening. 
     The lock nut 1 having the foregoing constitution can be used, particularly for setting the rolling bearing on a shaft. The shaft is formed, at its circumferential surface, with a male thread 8 having a small thread pitch for setting the rolling bearing properly. Correspondingly, the female thread 10 formed on the inner circumferential surface of the lock nut 1 also has a small thread pitch. The annular flat plate 3 has at its inner circumference with the arcuate protrusion 7 of about 270° angle, and the top end 9 of the protrusion 7 is formed such that it firmly contacts to the threaded surface of the male thread 8 on the shaft and applies interference pressure on the threaded surface. Consequently, upon screw-engagement of the round nut 1 to the shaft having the male thread 8, the plate 3 securely prevents the nut 1 from being loosened due to the rotations and the vibrations of the shaft, so that the nut 1 securely fixes the rolling bearing mounted on the shaft. 
     The arcuate protrusion formed on the annular flat plate 3 is not necessarily limited only to the arc of 270° angle but it may be extended inwardly from the portion corresponding to one-half or more of the inner circumference of the circumferential periphery 6. As shown in FIG. 5, an arcuate protrusion 7&#39; having 180° angle may be formed to the annular flat plate. 
     The arcuate protrusion 7 with 270° angle is formed to the annular flat plate 3 in the case where the nut has a low-pitched thread, for example, a fine thread or an extra fine thread. Alternatively, the arcuate protrusion 7&#39; with 180° angle is formed to the annular flat plate 3 in the case where the nut has a high-pitched thread, for example, a coarse thread. Accordingly, the protrusion 7 or 7&#39; deforms elastically but not plastically upon screw-engagement of the lock nut 1 with the thread member, for example, a shaft having a male thread or a bolt. 
     Since the annular flat plate 2 is formed with resilient material such as sheet metal for spring, if the arc width is suitably selected depending upon the thread pitch, the arcuate protrusion 4 is deformed always within the limit of elasticity and the interferring pressure thereof will not be reduced even after repeated screw-engagement of the lock nut with the thread member. 
     In addition, the sheet metal for spring used for the annular flat plate is made of a spring steel possessed a high strength and the sheet metal for spring usually has higher hardness than the member of the male thread. Accordingly, the threaded surface of the male thread member is not damaged if it is heat-treated upon screw-engagement of the lock nut according to this invention with the male thread member, while the threaded surface of the male thread member not applied with the heat treatment tends to be damaged easily upon screw-engagement of the lock nut according to this invention with the male thread member. In such a case, as shown in FIG. 9, a contacting member 13 made of soft metal, rubber or plastic may be secured to the top end 12 of the arcuate protrusion 7 or 7&#39; of the annular flat plate 3, wherein the protruding length of the protrusion 7 or 7&#39; is set to such an extent as the contacting member 13 slightly contacts to the root 11 of the male thread 8. As the result, the threaded surface of the male thread member made of a soft material can be prevented from being damaged. 
     The lock nut according to this invention may be formed, in addition to the foregoing round shape, to various other configurations such as a square nut or a hexagon nut. For example, it may be formed into a hexagon nut 15 as shown in FIG. 10 and FIG. 11. The hexagon nut 15 is formed at the upper portion thereof with a cylindrical portion 16 in which an annular flat plate 17 is secured by caulking said portion 16, and an arcuate protrusion 19 is formed to the inner circumference 18 of the annular flat plate 17 in the same manner as stated previously. In a case where the hexagon nut 15 has, for example, a fine thread, since the thread pitch formed to the thread member such as a bolt is small, an arcuate protrusion 19 is protruded from the portion corresponding to about 3/4 of the inner circumference 18 of the annular flat plate 17, and the top end 20 of the protrusion 19 is formed so as to contact to the flank surface or the root of the thread of the thread member. 
     The hexagon nut 15 having such a constitution is screwed with the male thread formed on the thread member and can surely set an article to be fastened disposed between the nut 15 and the thread member, whereby the hexagon nut 15 is prevented from being loosened due to the vibrations of the fastened article. 
     The annular flat plate may be formed as an annular flat plate 21 as shown in FIG. 12 to FIG. 16. The annular flat plate 21 is substantially similar to the annular flat plate 7 or 17 described before. But the annular flat plate 21 shown in FIG. 12 has projections 23 on the circumferential periphery 22. It is preferred to provide a plurality of projections 23 symmetrically on the circumferential periphery 22. 
     Upon securing of the annular flat plate 21 between the upper surface 2 and the cylindrical portion 4 of the nut by the caulking of the cylindrical portion 4, the projections 23 are enforced into the top end portion 24 of the cylindrical portion 4 so that the projections 23 are engaged with the top and portion 24 as shown in FIG. 17. Accordingly, the annular flat plate 21 can surely be secured between the upper surface 2 and the cylindrical portion 4 of the nut to more surely prevent the annular flat plate 21 from sliding movement relative to the nut 1. 
     The annular flat plate 21 has a single arcuate protrusion 25 of a large surface area and receives considerably great rotational force from the male thread member B upon screw-engagement of the nut 1 with the male thread member B, but since the annular flat plate 21 has the projections 23, the plate 21 does not cause sliding movement relative to the nut 1. 
     The annular flat plate 21 shown in FIG. 14 has projections 26 on the circumferential periphery 22, in which a plurality of projections 26 are, preferably, extended radially on the circumferential periphery 22 and formed symmetrically thereon. 
     When the annular flat plate 21 is secured between the upper surface 2 and the cylindrical portion 4 of the nut 1 by the caulking of the cylindrical portion 4, the projections 26 are enforced into the top end portion 24 of the cylindrical portion 4 as shown in FIG. 18 and FIG. 19. Consequently, the annular flat plate 21 is secured between the upper surface 2 and the cylindrical portion 4, whereby the relative sliding movement of the annular flat plate 21 to the nut 1 can be prevented. 
     Should the annular flat plate 21 move relatively to the nut 1 upon screw-engagement of the nut 1 with the male screw member B, the locking effect of the lock nut 1 would be decreased substantially. Since the projections 23 or 26 are provided to the annular flat plate 21, the relative sliding movement of the annular flat plate 21 to the nut 1 can surely be prevented, whereby the locking effect of the lock nut 1 can be ensured. 
     Such projections 23 or 26 may be provided on the circumferential periphery 6 of the annular flat plate 3 or on the circumferential periphery of the annular flat plate 17.